1. Field of the Invention
The present invention relates to a reaction method using a microreactor, particularly to an apparatus which manufactures materials and products in the fields of the chemical industry and medical product industry, and more particularly to a reaction method using a microreactor by the reaction of fluids which causes a plurality of fluids to join together in one reaction channel via respective fluid supply routes, whereby these fluids are caused to flow as laminar flows in the shape of thin layers and the fluids are diffused together in a normal direction of contact interfaces thereof to cause a reaction.
2. Description of the Related Art
In recent years, in the chemical industry and the medical product industry related to the manufacturing of medical products, reagents, etc., the development of new manufacturing processes using a microcontainer called a micromixer or microreactor has been pushed forward with. A micromixer or microreactor is provided with a microspace (reaction channel) which leads to a plurality of fine fluid supply routes, the equivalent diameter (circle-equivalent diameter) obtained when the section of the microspace (reaction channel) is converted to a circle being several micrometers to several hundreds of micrometers. By causing a plurality of fluids to flow together in the microspace through the plurality of fluid supply routes, the plurality of fluids are mixed together or caused to produce a chemical reaction simultaneously with the mixing. It is considered that a micromixer and a microreactor are common in their basic structure. In some cases, however, a microcontainer which mixes a plurality of fluids together is called a micromixer and a microcontainer which causes a chemical reaction during the mixing of a plurality of fluids is called a microreactor. Therefore, a microreactor of the present invention includes a micromixer.
There are examples of such a microreactor, for example, in PCT International Unexamined Patent Publication No. WO 00/62913, National Publication of International Patent Application No. 2003-502144 and Japanese Patent Application Publication No. 2002-282682. In all of these microreactors, two kinds of fluids are caused to flow through respective very fine fluid supply routes and introduced into a microspace as laminar flows in the form of a very thin layer, and in this microspace the two kinds of fluids are mixed together and caused to react with each other.
Next, points where the reaction by a microreactor as described above differs from batch type mixing and reaction by use of a stirring tank etc. will be described below. That is, because in general a chemical reaction occurs when molecules encounter each other at the interfaces of reaction fluids, when a reaction occurs in a microspace, the area of the interface increases relatively and the reaction efficiency increases remarkably. Furthermore, for the diffusion of molecules itself, the reaction time is in proportion to the square of distance. This means that as the scale of a microspace is reduced, mixing proceeds accordingly due to the diffusion of molecules even when the reaction fluids are not positively mixed, with the result that the reaction tends to occur easily. Furthermore, in a microspace, because of the small scale, the flow is dominated by laminar flows and the fluids diffuse in a laminar flow state while flowing in a direction orthogonal to the flow.
When such a microreactor is used, it is possible to perform the high-accuracy control of the reaction time and reaction temperature of fluids in comparison with, for example, a conventional batch method which uses a large-volume tank etc. as a field of reaction. In the case of a batch type method, particularly for fluids of rapid reaction time, the reaction proceeds on the reaction contact surfaces in the initial stage of mixing and furthermore primary products formed by the reaction of the fluids with each other continue to be subjected to the reaction within the tank, with the result that nonuniform reaction products may be produced. In contrast to this, in the case of a microreactor, fluids flow continuously without being resident within the microspace and hence primary products formed by the reaction of fluids with each other do not continue to be subjected to the reaction within the microspace. Therefore, it becomes possible to take out even pure primary products which have not hitherto been easily taken out.
When a chemical substance which has hitherto been manufactured in a small amount by use of an experimental production facility is to be manufactured in a large amount by use of a scaled up large-scale production facility, much labor and time have so far been required in order to obtain reproducibility in the batch type large-scale production facility in comparison with the experimental production facility. Owing to the concept of numbering up of the parallel arrangement of manufacturing lines using a microreactor according to the production amount, it is possible to substantially reduce the labor and time for obtaining this reproducibility.
Incidentally, because in a microreactor, the substance diffusion which involves the diffusion of fluids in a normal direction of contact surfaces of the fluids is basic to the reaction, the opening width of a reaction channel, which is the microspace, i.e., the distance orthogonal to the flow of fluids determines the characteristics of the reaction. And the fluids are caused to flow (be resident) within the reaction channel in such a manner that the diffusion and reaction of the fluids at the discharge port of the microreactor are completed according to the characteristics of the reaction. When a microreactor designed on the basis of such a basic principle is incorporated in a manufacturing process, because the opening width of the reaction channel is optimally designed according to the reaction characteristics (diffusion rate and reaction rate) of the fluids, it is impossible to cause an optimum reaction if fluids of different reaction characteristics are intended for a reaction with the same microreactor. Even if a reaction is made possible to some extent, the range of possible reaction changes, condition changes or changes of the product characteristics are greatly limited. Therefore, it is necessary to perform operations, such as using the manufacturing line as a dedicated line and replacing the microreactor with an appropriate one according to the reaction and conditions or product characteristics, providing the disadvantage that equipment cost rises and time losses due to replacement occur.
Furthermore, what poses a problem in a case where a reaction involving coagulation and precipitation occurs in the reaction channel is that coagulated matter and precipitates formed by the reaction adhere to the wall surface of the reaction channel and are deposited on it, thereby clogging the reaction channel. Although in order to prevent this there is available a method which involves performing surface treatment for preventing coagulated matter and precipitates from adhering to the wall surface of the reaction channel, for example, coating this wall surface with a coating agent, the effect of a coating agent on the prevention of adhering differs depending on the kinds of coagulated matter and precipitates and, therefore, different coating agents must be used according to the fluids handled. This is not an essential solution. As described above, a reaction obtained by use of a conventional microreactor has the defect that clogging troubles occur frequently and the disassembly cleaning to eliminate clogging troubles must be frequently performed.